Question

Indicate the number of protons and neutrons in the following nuclei: \((\mathbf{a}) _{24}^{56} \mathrm{Cr},(\mathbf{b})^{193} \mathrm{Tl},(\mathbf{c})\) argon-\(38.\)

Short answer

a. Chromium-56: \(24\) protons and \(32\) neutrons. b. Thallium-193: \(81\) protons and \(112\) neutrons. c. Argon-38: \(18\) protons and \(20\) neutrons.

Step-by-step solution

a. Chromium-56

The atomic number for Chromium is 24 (notated as the lower number), which means it has 24 protons. To find the number of neutrons, we subtract the atomic number from the mass number (56 - 24), which gives us 32 neutrons.

b. Thallium-193

First, we need to determine the atomic number for Thallium, which is 81. This can be found in a periodic table. With the atomic number 81, Thallium has 81 protons. To find the number of neutrons, we subtract the atomic number from the mass number (193 - 81), giving us 112 neutrons.

c. Argon-38

The atomic number for Argon is 18 (notated as the lower number), which means it has 18 protons. To find the number of neutrons, we subtract the atomic number from the mass number (38 - 18), which gives us 20 neutrons.

Key concepts

Protons

Protons are subatomic particles found in the nucleus of an atom. They carry a positive electrical charge. This makes them essential components of atomic structure. The number of protons in an atom defines what element it is and determines its atomic number.
Dominantly, protons help stabilize the atom by balancing out the negative charge of electrons, which circle the nucleus. For example, a chromium atom always has 24 protons, which you can find in the periodic table as its atomic number.

• Always positively charged.
• Determine the element's identity and its chemical properties.
• Balance electron charge in neutral atoms.

Knowing how to find the number of protons helps understand atomic structure and chemical behavior.

Neutrons

Neutrons are electrically neutral particles found in the nucleus alongside protons. Unlike protons, neutrons do not carry a charge. They play a crucial role in the stability of an atom. Atoms with too few or too many neutrons can become unstable, leading to radioactive decay.
Neutrons add mass to the atom but do not affect its chemical properties like the protons do. Calculating neutrons involves subtracting the atomic number from the mass number. For instance, in thallium with a mass number of 193 and 81 protons, there are 112 neutrons (193 - 81 = 112).

• No electrical charge.
• Adds to the atomic mass.
• Affects stability of nucleus.

Understanding neutron count is key to studying isotopes and nuclear reactions.

Atomic Number

The atomic number is a fundamental property of an element that determines its position in the periodic table. It is equal to the number of protons in the nucleus of an atom.
This number not only provides insight into the element's identity, but it also dictates the number of electrons in a neutral atom, ensuring the atom's electrical neutrality. For example, argon has an atomic number of 18, indicating it has 18 protons and, in an uncharged state, 18 electrons.

• Clearly identifies the element (e.g., Argon is atomic number 18).
• Dictates electronic configuration.
• Unique to each element.

Through its pivotal role, the atomic number lays the groundwork for understanding an element’s chemical behavior.

Mass Number

The mass number of an atom is the total count of protons and neutrons in the nucleus. It is an integer value and differs across isotopes of an element as the number of neutrons can vary while the protons remain constant.
This concept is crucial for calculations involving the nucleus, such as identifying isotopes and understanding nuclear reactions. For a nucleus to be given as chromium-56, the mass number is 56, which is the sum of its 24 protons and 32 neutrons (56 - 24 = 32).

• Equals protons plus neutrons.
• Varies across different isotopes of the same element.
• Influences atomic mass but not chemical identity.

Mastery of mass number concepts aids in tackling more complex topics like nuclear chemistry.